Closed-loop precoding techniques have been introduced into a Long Term Evolution (LTE) Release 8 (Rel-8) system to improve spectral efficiency. For the closed-loop precoding technique, it is required to store an identical set of precoding matrices both in a base station and a terminal in advance, and the set of precoding matrices is referred to as a code book. After estimating channel information in accordance with a cell common pilot, the terminal selects a precoding matrix from the code book in accordance with a predetermined criteria. The predetermined criteria may be maximization of mutual information or maximization of Signal-to-Interference plus Noise Ratio (SINR). An index of the selected precoding matrix in the code book is fed back by the terminal to the base station via an uplink channel, and the index is used as Precoding Matrix Indicator (PMI). The base station may determine the precoding matrix used by the terminal in accordance with the received PMI.
For the closed-loop precoding technique, a transmission parameter is selected on the basis of feedback information from the terminal, so in the case that the terminal moves at a high speed, the PMI fed back by the terminal may probably be invalid, i.e., it is not able to reflect a current channel state of the terminal. In this case, the transmission parameter may not match an actual channel condition, and a system performance may be deteriorated. To solve problems in a high-speed movement scenario, an open-loop Multiple Input Multiple Output (MIMO) transmission scheme has been introduced into the LTE Rel-8 system. For the open-loop MIMO transmission scheme, the terminal does not return the PMI any more, and instead, it is merely necessary for the terminal to return information about a Channel Quality Indicator (CQI) and a Rank Indicator (RI). When the terminal calculates the CQI and the RI, it is assumed that the terminal uses a pre-agreed precoding matrix on a resource involved in the data transmission.
In a word, it is impossible for the open-loop MIMO transmission scheme to adaptively adjust the transmission parameter in accordance with a channel change, so it is impossible to obtain a beamforming gain and a precoding gain. In addition, for a closed-loop MIMO transmission scheme, since the information fed back by the terminal is invalid in the case that the terminal moves at a high speed, the transmission parameter does not match the actual channel condition, which may cause the system performance to be deteriorated.